<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body{
            margin:0;
        }
        .left,.right,.middle{
            float:left;
            height:100px;
        }
        .middle{
            width:100%;
        }
        .left{
            width:200px;
            background:saddlebrown;
            margin-left:-100%;
        }
        .right{
            width:200px;
            background:seagreen;
            margin-left:-200px;
        }
        .content{
            background:lightcoral;
            height:200px;
            margin-left:200px;
            margin-right:200px;
        }
    </style>
</head>
<body>
    <div class="main">
        <div class="middle">
            <div class="content"></div>
        </div>
        <div class="left">left</div>
        <div class="right">right</div>
    </div>
</body>
</html>